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Perrin A, Métay C, Savarese M, Ben Yaou R, Demidov G, Nelson I, Solé G, Péréon Y, Bertini ES, Fattori F, D'Amico A, Ricci F, Ginsberg M, Seferian A, Boespflug-Tanguy O, Servais L, Chapon F, Lagrange E, Gaudon K, Bloch A, Ghanem R, Guyant-Maréchal L, Johari M, Van Goethem C, Fardeau M, Morales RJ, Genetti CA, Marttila M, Koenig M, Beggs AH, Udd B, Bonne G, Cossée M. Titin copy number variations associated with dominant inherited phenotypes. J Med Genet 2024; 61:369-377. [PMID: 37935568 PMCID: PMC10957311 DOI: 10.1136/jmg-2023-109473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 10/18/2023] [Indexed: 11/09/2023]
Abstract
BACKGROUND Titinopathies are caused by mutations in the titin gene (TTN). Titin is the largest known human protein; its gene has the longest coding phase with 364 exons. Titinopathies are very complex neuromuscular pathologies due to the variable age of onset of symptoms, the great diversity of pathological and muscular impairment patterns (cardiac, skeletal muscle or mixed) and both autosomal dominant and recessive modes of transmission. Until now, only few CNVs in TTN have been reported without clear genotype-phenotype associations. METHODS Our study includes eight families with dominant titinopathies. We performed next-generation sequencing or comparative genomic hybridisation array analyses and found CNVs in the TTN gene. We characterised these CNVs by RNA sequencing (RNAseq) analyses in six patients' muscles and performed genotype-phenotype inheritance association study by combining the clinical and biological data of these eight families. RESULTS Seven deletion-type CNVs in the TTN gene were identified among these families. Genotype and RNAseq results showed that five deletions do not alter the reading frame and one is out-of-reading frame. The main phenotype identified was distal myopathy associated with contractures. The analysis of morphological, clinical and genetic data and imaging let us draw new genotype-phenotype associations of titinopathies. CONCLUSION Identifying TTN CNVs will further increase diagnostic sensitivity in these complex neuromuscular pathologies. Our cohort of patients enabled us to identify new deletion-type CNVs in the TTN gene, with unexpected autosomal dominant transmission. This is valuable in establishing new genotype-phenotype associations of titinopathies, mainly distal myopathy in most of the patients.
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Affiliation(s)
- Aurélien Perrin
- Laboratoire de Génétique Moléculaire, Centre Hospitalier Universitaire de Montpellier, Montpellier, France
- PhyMedExp, Université de Montpellier, INSERM, CNRS, Montpellier, France
| | - Corinne Métay
- Unité Fonctionnelle de Cardiogénétique et Myogénétique moléculaire et cellulaire, Centre de Génétique Moléculaire et Chromosomique, Groupe Hospitalier La Pitié-Salpêtrière-Charles Foix, Paris, France
- Sorbonne Université, INSERM, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Marco Savarese
- Tampere Neuromuscular Center, Folkhälsan Research Center, Helsinki, Finland
| | - Rabah Ben Yaou
- Sorbonne Université, INSERM, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - German Demidov
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tubingen, Germany
| | - Isabelle Nelson
- Sorbonne Université, INSERM, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Guilhem Solé
- CHU de Bordeaux, AOC National Reference Center for Neuromuscular Disorders, Bordeaux, France
| | - Yann Péréon
- Department of Clinical Neurophysiology, Reference Centre for Neuromuscular Diseases AOC, Filnemus, Euro-NMD, CHU Nantes, Nantes Université, Place Alexis-Ricordeau, Nantes, France
| | - Enrico Silvio Bertini
- Unit of Muscular and Neurodegenerative Disorders, Bambino Gesù Children Research Hospital, IRCCS, Rome, Italy
| | - Fabiana Fattori
- Unit of Muscular and Neurodegenerative Disorders, Bambino Gesù Children Research Hospital, IRCCS, Rome, Italy
| | - Adele D'Amico
- Unit of Muscular and Neurodegenerative Disorders, Bambino Gesù Children Research Hospital, IRCCS, Rome, Italy
| | - Federica Ricci
- Division of Child and Adolescent Neuropsychiatry, University of Turin, Turin, Italy
| | - Mira Ginsberg
- Department of Pediatric Neurology, Wolfson Medical Center, Holon, Israel
| | | | - Odile Boespflug-Tanguy
- Institut I-MOTION, Hôpital Armand Trousseau, Paris, France
- UMR 1141, INSERM, NeuroDiderot Université Paris Cité and APHP, Neuropédiatrie, French Reference Center for Leukodystrophies, LEUKOFRANCE, Hôpital Robert Debré, Paris, France
| | - Laurent Servais
- Institut I-MOTION, Hôpital Armand Trousseau, Paris, France
- MDUK Oxford Neuromuscular Centre & NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, UK
- Neuromuscular Reference Center, Division of Paediatrics, University and Hospital University of Liège, Liège, Belgium
| | - Françoise Chapon
- Département de pathologie, Centre de Compétence des Maladies Neuromusculaires, Centre Hospitalier Universitaire de Caen, Caen, France
| | - Emmeline Lagrange
- Centre de Compétences des Maladies Neuro Musculaires, Centre Hospitalier Universitaire Grenoble Alpes, Grenoble, France
| | - Karen Gaudon
- Unité Fonctionnelle de Cardiogénétique et Myogénétique moléculaire et cellulaire, Centre de Génétique Moléculaire et Chromosomique, Groupe Hospitalier La Pitié-Salpêtrière-Charles Foix, Paris, France
| | - Adrien Bloch
- Unité Fonctionnelle de Cardiogénétique et Myogénétique moléculaire et cellulaire, Centre de Génétique Moléculaire et Chromosomique, Groupe Hospitalier La Pitié-Salpêtrière-Charles Foix, Paris, France
| | - Robin Ghanem
- Unité Fonctionnelle de Cardiogénétique et Myogénétique moléculaire et cellulaire, Centre de Génétique Moléculaire et Chromosomique, Groupe Hospitalier La Pitié-Salpêtrière-Charles Foix, Paris, France
| | | | - Mridul Johari
- Tampere Neuromuscular Center, Folkhälsan Research Center, Helsinki, Finland
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia
| | - Charles Van Goethem
- Laboratoire de Génétique Moléculaire, Centre Hospitalier Universitaire de Montpellier, Montpellier, France
- Montpellier BioInformatique pour le Diagnostic Clinique (MOBIDIC), Plateau de Médecine Moléculaire et Génomique (PMMG), CHU Montpellier, Montpellier, France
| | - Michel Fardeau
- Sorbonne Université, INSERM, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Raul Juntas Morales
- Department of Neurology, Hospital Universitario Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Casie A Genetti
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Minttu Marttila
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
- HiLIFE Helsinki Institute of Life Science, Tukholmankatu 8, FI-00014, University of Helsinki, Helsinki, Finland
| | - Michel Koenig
- Laboratoire de Génétique Moléculaire, Centre Hospitalier Universitaire de Montpellier, Montpellier, France
- PhyMedExp, Université de Montpellier, INSERM, CNRS, Montpellier, France
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Bjarne Udd
- Tampere Neuromuscular Center, Folkhälsan Research Center, Helsinki, Finland
| | - Gisèle Bonne
- Sorbonne Université, INSERM, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Mireille Cossée
- Laboratoire de Génétique Moléculaire, Centre Hospitalier Universitaire de Montpellier, Montpellier, France
- PhyMedExp, Université de Montpellier, INSERM, CNRS, Montpellier, France
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Manivannan SN, Darouich S, Masmoudi A, Gordon D, Zender G, Han Z, Fitzgerald-Butt S, White P, McBride KL, Kharrat M, Garg V. Novel frameshift variant in MYL2 reveals molecular differences between dominant and recessive forms of hypertrophic cardiomyopathy. PLoS Genet 2020; 16:e1008639. [PMID: 32453731 PMCID: PMC7274480 DOI: 10.1371/journal.pgen.1008639] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 06/05/2020] [Accepted: 01/29/2020] [Indexed: 12/18/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is characterized by thickening of the ventricular muscle without dilation and is often associated with dominant pathogenic variants in cardiac sarcomeric protein genes. Here, we report a family with two infants diagnosed with infantile-onset HCM and mitral valve dysplasia that led to death before one year of age. Using exome sequencing, we discovered that one of the affected children had a homozygous frameshift variant in Myosin light chain 2 (MYL2:NM_000432.3:c.431_432delCT: p.Pro144Argfs*57;MYL2-fs), which alters the last 20 amino acids of the protein and is predicted to impact the most C-terminal of the three EF-hand domains in MYL2. The parents are unaffected heterozygous carriers of the variant and the variant is absent in control cohorts from gnomAD. The absence of the phenotype in carriers and the infantile presentation of severe HCM is in contrast to HCM associated with dominant MYL2 variants. Immunohistochemical analysis of the ventricular muscle of the deceased patient with the MYL2-fs variant showed a marked reduction of MYL2 expression compared to an unaffected control. In vitro overexpression studies further indicate that the MYL2-fs variant is actively degraded. In contrast, an HCM-associated missense variant (MYL2:p.Gly162Arg) and three other MYL2 stop-gain variants (p.E22*, p.K62*, p.E97*) that result in loss of the EF domains are stably expressed but show impaired localization. The degradation of the MYL2-fs can be rescued by inhibiting the cell’s proteasome function supporting a post-translational effect of the variant. In vivo rescue experiments with a Drosophila MYL2-homolog (Mlc2) knockdown model indicate that neither the MYL2-fs nor the MYL2:p.Gly162Arg variant supports normal cardiac function. The tools that we have generated provide a rapid screening platform for functional assessment of variants of unknown significance in MYL2. Our study supports an autosomal recessive model of inheritance for MYL2 loss-of-function variants in infantile HCM and highlights the variant-specific molecular differences found in MYL2-associated cardiomyopathy. We report a novel frameshift variant in MYL2 that is associated with a severe form of infantile-onset hypertrophic cardiomyopathy. The impact of the variant is only observed in the recessive form of the disease found in the proband and not in the parents who are carriers of the variant. This contrasts with other dominant variants in MYL2 that are associated with cardiomyopathies. We compared the stability of this variant to that of other cardiomyopathy associated MYL2 variants and found molecular differences that correlated with disease pathology. We also show different protein domain requirements for stability and localization of MYL2 in cardiomyocytes. Furthermore, we used a fly model to demonstrate functional deficits due to the variant in the developing heart. Overall, our study shows a molecular mechanism by which loss-of-function variants in MYL2 are recessive while missense variants are dominant. We highlight the use of exome sequencing and functional testing to assist in the diagnosis of rare forms of disease where pathogenicity of the variant is not obvious. The new tools we developed for in vitro functional study and the fly fluorescent reporter analysis will permit rapid analysis of MYL2 variants of unknown significance.
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Affiliation(s)
- Sathiya N. Manivannan
- Center for Cardiovascular Research, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Heart Center, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
| | - Sihem Darouich
- University of Tunis El Manar, Faculty of Medicine of Tunis, LR99ES10 Laboratory of Human Genetics, Tunis, Tunisia
- * E-mail: (SD); (VG)
| | - Aida Masmoudi
- University of Tunis El Manar, Faculty of Medicine of Tunis, Department of Embryo-Fetopathology, Maternity and Neonatology Center, Tunis, Tunisia
| | - David Gordon
- Institute for Genomic Medicine at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
| | - Gloria Zender
- Center for Cardiovascular Research, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
| | - Zhe Han
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Sara Fitzgerald-Butt
- Center for Cardiovascular Research, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Heart Center, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States of America
| | - Peter White
- Institute for Genomic Medicine at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States of America
| | - Kim L. McBride
- Center for Cardiovascular Research, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Heart Center, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States of America
| | - Maher Kharrat
- University of Tunis El Manar, Faculty of Medicine of Tunis, LR99ES10 Laboratory of Human Genetics, Tunis, Tunisia
| | - Vidu Garg
- Center for Cardiovascular Research, Abigail Wexner Research Institute at Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Heart Center, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States of America
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail: (SD); (VG)
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